78166409 has 2 divisors, whose sum is σ = 78166410. Its totient is φ = 78166408.

The previous prime is 78166381. The next prime is 78166433. The reversal of 78166409 is 90466187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73479184 + 4687225 = 8572^2 + 2165^2 .

It is a cyclic number.

It is not a de Polignac number, because 78166409 - 2¹² = 78162313 is a prime.

It is a super-2 number, since 2×78166409² = 12219974991910562, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78166009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39083204 + 39083205.

It is an arithmetic number, because the mean of its divisors is an integer number (39083205).

Almost surely, 2^78166409 is an apocalyptic number.

It is an amenable number.

78166409 is a deficient number, since it is larger than the sum of its proper divisors (1).

78166409 is an equidigital number, since it uses as much as digits as its factorization.

78166409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72576, while the sum is 41.

The square root of 78166409 is about 8841.1769012954. The cubic root of 78166409 is about 427.5695022823.

The spelling of 78166409 in words is "seventy-eight million, one hundred sixty-six thousand, four hundred nine".